1. Field
Certain embodiments generally relate to communication systems and, in particular, may relate to millimeter wave (mmWave) communications.
2. Description of the Related Art
A global bandwidth shortage facing wireless carriers has motivated the consideration of the underutilized millimeter wave (mmWave) frequency spectrum for future broadband cellular communication networks. mmWave (or extremely high frequency) generally refer to the frequency range between 30 and 300 gigahertz. This is the highest radio frequency band in practical use today. Radio waves in this band have wavelengths from ten to one millimeter, giving it the name millimeter band or millimeter wave.
mmWave systems will be characterized by higher propagation loss than lower frequencies. To combat this higher loss mmWave systems will employ antenna arrays with a large number of elements especially at the access point. The large arrays overcome the higher propagation loss by concentrating the energy in the best direction to the mobile through the use of narrow beams. Since mmWave systems will be characterized by high bandwidths, the analog to digital converters (ADCs) and digital to analog converters (DACs) will use extreme amounts of power. To minimize power consumption typically only a single ADC and DAC will be used for all antennas in one array meaning the beamforming will need to be done at radio frequency (RF). Besides data transmissions these narrow beams may need to be used for other transmissions such as for initial acquisition of timing and frequency. The use of these narrow beams at RF makes the use of existing acquisition methods difficult and inefficient, hence there is a need for an efficient method of initial acquisition for mmWave communications.